Pressure gauge



March 6, w M SH PRESSURE GAUGE Filed Nov. 15, 1942' Fig.1

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John W. Marsh "f n/5 JQ a @54 E /Z a. aw

meme Mir. s, 1945 invention describedv hereinvmaybemanui'actured-and-used by or for the Governmentior overnmentalpurposes, without-payment to me 5 indicated pressure range.

usual constructions the, gaugeiaceZis v "into equalpportions, providing.equal-. angular movementsof theindicating hand forltheoentire handltravel. In, this type oi constructior i, qrthe gauge movement usually,consists of 1 circularcgear,

- membersywhich: actuate-the indicatingxhand: "On

gauges otthis type,- when usedain'cconnection with high pressureapparatuaxthe constant: angular movement f the indicating hand is not'adapted to indicate small .variations in-r pressure because;

7 of the relativelyshort distance lbetween 'dial calibrations: and therelatively.ishortaangular movement'adapted toxcover. this shortdistanc'e'. I; am awarei that; gauges haver-been'h'devisedwwhichshow-onlya portion 0! the pressure: range, I land. that gaugeshave @been devised which 'have an indicating-hand. adaptedzto traversethe whole pressure .xscaiei and "a" second :rindicating hand adapted--to traverse a an enlarged portion of the pressure scale showingsmallervariations in pressure. A disadvantage oi the" flrst type gaugementioned" is that it i dos -notindi'cate pressure Jnuch above-or belowthe 'operatirig "rangeg -and a disadvantage of the second type gaugementioned is that more than s 'one movement is: "requiredto. actuatethe-multiple indic'ating hands. 7 vBy mydevice; movement is imparted tothemdicating hand of a gauge so that said hand mo'ves relatively slowlyin certaini..portions of -the pressure range and relatively rapidly in-that portion of the-pressure range'riniwhich the operatof-isinterested. .,.This is accomplished 'bysubstituting for the usualcircular gear construction, anonannularqgear construction such as aspairot ellipo tical; gears or elliptical rsectors. LThe-gau'ge' dialcalibrations -.are yspaced -;1inaccordance with the travel oftheindicatinghancl with :the "result that the; widest spacings occur inthe; range. of ii'astest handtravel therei'ore aiiording-a maximumsensitivity; ot the gauge @170 minor pressure variations.inthis ranger;I I Accordin y it is;an object of thegpresent'ine vention provide amechanical movement tf-for agauge 'f cause movement a (eras-rippletimwijmj Unmisutd than; I entree-intimate v,iria" handof'aiaue adaptedto movesaid indi- ,calih ratedgauge ,dial-, ;and l3, indicates the frontcover plateupon wthich the gauge dial is mounted. These elements, from;themethod of califro'nt vplate indicated ingbroken outline.- .1. v2.

Another 1 objector -present invention -.to provide a mQWmmtior; th ndcating'hand of a pressure gauge adapted to provide maximum travei oitheindicating handouring a mph-aware inthe claims .ap-

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gauge containing mechanical -movement with portions'ror thexaugelasagauge dialandsgauge L howing thfihtiiorIoi-s Figs. zjw 4; inlusiveare d agrammatic reprei i e it t o slshowinag positionofthe-indicating hand for various operative ,chanicai movement positionsofithei me- Referring to 1; lo

n the eaug e casing, N; indicates the gauge glass, 1.2 indicatesthebrating'the gauge dial, for'm no part of the pres-'- ent invention andmaybe of: conventional design.

' In: order that gauge maybeconnected'Qto ,f Another have;semitesimnteaiams t an .a source or; pre sure,;8uch,as fsteam :line, apressure inlet fittinggllis provided. Inle't} l4 feeds ,into a pair of 1eelfedrainingetype' Bourdon tubes J5 and it which serve asthez-pressure'responsive elements {of my gaugesvg'lubes lland "are of conventional.oval cross-section and have at their respective ends fittings 11' and 23which close oil 1the-tubesand serve to connect them to the'linkagesystemto.be'described'hereaiter. I f Links:,r.l 9,:2l-, and .25;'and lever 2Tforr'n the main elements of thesyatem which I'jisetotraii's mit motiorr: from i: the Bourdon tubes "=1 5- and l 6 and; arebroadly referred as the linkage system. Fitting I'I onrtube "1 I isconnectedpivotally at law link It at its. bther' end; link le 155m turn,pivotallyi connectedat illz I: A I proximately at the center of link2l,"th'ere is p'rk a p ot 22 to which-isgconnectedfitting? on 1 tubeul8; s; link! I i "a third -'*pivot p om1;, namely 'll, tol which link-iiis also. connected. At itsopposite" end, linkfliiis Latin vtojloneiendof lever; I

unann nc d iLever .21 1 contains aslot 2I which eittendssuh stantiallythe len'zth or the lever} l Within this slot, and substantially at theend oi lever 3'! opposite that on which pivot It is mounted. there iscontained a lever iulcrmn 23 which is attached to the bell crank shapedmember 33. Member 30 is stationary and is attached at 3| by rivet orotherwise to the gall!!! casing ll. Member 33 also contains a shaft 33which serves as a pivot for elliptical gear member 33.

The linkage system just described transmits motion from Bourdon tubes IIand It to the mechanical movement for the indicating hand 33 oi whichmovement elliptical sector 31 and elliptical gear 33 form the mainelements. Elliptical sector 31 is pivotally supported on shaft 33 and isprovided with radial arms 33. On the radial arm 3! which forms the majorradius of sector 31 there is mounted a projecting pin ll which proiectsinto slot It in lever 21 and which is contacted by the sides of slot 23when lever 21 moves.

The periphery of sector 31 containsgear teeth 3| which mesh with thegear teeth 33 on elliptical pinion 33 whereby motion is imparted to thelatter when sector 31 rotates. Rigidly aiilxed to pinion 34, by means ofcollar I, is indicating hand 33 which rotates about shaft 32 when pinion33 rotates.

The operation of my invention is as follows:

when a source 01' pressure is admitted through fitting l4 andconsequently to Bourdon tubes II and it, these tubes then expand or bendoutwardly in a manner well known to the art-with the result that tube Itacting through pivot It tends to pull link it to the left and upward andtube It acting through pivot 22 tends topull link 2| to the right andupward. The action or the individual tubes l and It results in movinglinks it, 21, and along a path which is the resultant of the forceexerted by the individual tubes. This resultant action causes link II,actuated through pivot 24, to move toward the right and slightly upwardwith the result that pivot is moved to the right.

When pivot 23 moves, lever 21 is pivoted counter-clockwise at fulcrum.23 and projection. 33, which is mounted on one of the radial arms 3! ofelliptical sector 31, is also moved counterclockwise with the resultthat elliptical sector 31 starts to turn in a counter-clockwisedirection about shaft 33.

As elliptical sector 31 turns, the elliptical pinion 34 also turns sinceboth sector 31 and pinion 34 are in gear meshingrelation through themedium or the gear teeth 3' and 33. Pinion 34 turns in a clockwisedirection thereby moving the indicating hand 83 across the calibrationson dial i2. At the start'oi the operating cycle, indicating hand 33moves slowly since substantialb the minor axis of the elliptical sector31 is in contact with substantially the major axis oi the ellipticalpinion 3|. As the. movement proceeds the rate of travel of theindicating hand 33 is increased until, when the major axis of theelliptical sector 31 is in line with the minor axis of the ellipticalpinion 34, it reaches a maximum speed. Asthe pressure increases further,theindicating hand 33 is driven past the point of maximum speed and thegear movement goes through a downward cycle during which the indicatinghand is moved at a decreasing rate of speed.

This action, 1. e., the pofltion of the indicating hand for variouspositions of the mechanical moving means, is illustrated in Figs. 2 to 4inclusive. As shown in Fig. 2 the indicating hand 33 is opposite thezeropoint on the dial ii. Indicating hand 33 is rigi ly aiiixed tocollar ll acme-rs which in turn is rigidly connected to ellipticalpinion 34 and elliptical pinion 34 is operativeiy connected to theelliptical driving sector 31. As described above, substantially themajor axis oi s the driven pinion 33 is in line with substantially theminor axis of driving sector 31 when indicating hand 33 is in theposition shown in Fig. 2.

As member 31 rotates in a counter-clockwise direction, driven member 34turns in a clockwise direction and the interacting motion of the twogear members results in a fast upswing of the indicating hand 33 until amaximum speed is reached when the members 3| and 31 are in the positionshown in Fig. 3. In this position the major axis of the driving member31 is in line with the minor axis oi the driven member 34.

As the member 31 continues to rotate in a counter-clockwise direction,driven member 34 is actuated at a decreasing rate of speed, just thereverse oi that occurring when member 34 went from the positionindicated in Fig. 2 to the position indicated in Fig. 3. When drivenmember 34 reaches the end of its travel as indicated in Fig. 4, theindicating hand 33 will be opposite the maximum pressure indication onthe dial l2 and the minor axis of the driving member 31 will once morebe substantially in line with the major axis of the driven member 33.

Dial l2, shown in Figs. 2 to 4 inclusive, and shown in part in Fig. l,is formed in circular shape and the calibrations thereof are alinedalong the arc of a circle. Since the movement of the indicating hand 33is variable, i. e., varying as the elliptical gear segments coact, thein- 35 dicating hand will have a greater travel for a given pressuredifference when the pressure is in the operating pressure range, i. e.,when the indicating hand 33 is in the center portion of the calibrationson dial it, from that which it will have when the pressure is eitherbelow or above said range. Consequently, the calibrations on dial 1!must be spaced progressively farther apart from the end calibrations tothe center calibrations at which point the indicating hand has itsgreatest speed of travel. The particular spacing of the dialcalibrations is obtained by converting the travel, for equal pressureincrements, oi a point along the periphery of a portion or an ellipse,substantially the length of the circular are, into travel along thecircular are for the same pressure increments. The space between theindividual dial calibrations will naturally depend upon the ratio of themajor axis of the ellipse to that 01' the minor axis. as will be evidentto one skilled in the art. Where this ratio closer together and thecenter calibrations farther apart than if the ratio were smaller. Wherethe variable speed motion is obtained by nonannular gears other thanelliptical gears, the 4 dial calibrations will simply be laid out inaccordance with the indicating hand travel obtained.

From the above description it will be seen that I have invented amechanical driving movement for the indicating hand of a pressure gaugewhich is adapted to drive said indicating hand at a variable rate ofspeed, the greatest speed being within the desired operating pressurerange. In this manner, the operator is enabled to detect smallvariations in pressure within the pressure range in which heisinterested since the dial calibrations have their maximum spacingwithin this pressure range. At the same time he is able to detect whenthe pressure goes to either side is large, the end calibrations willnaturally be of this desired pressure range. Although devices whichimpart a variable speed to the indicating hand of a pressure gauge areknown, these devices are generally designed to impart a con stantlyincreasing or constantly decreasing speed of travel to the indicatinghand. Such an arrangement may be used where the pressure increasesaccording to a certain mathematical function such as a logarithmically.In my device I provide a maximum speed position intermediate minimumspeed positions so that the greatest utilization of the gauge can beobtained in the range in which the operator-is primarily interested.

Although I have disclosed an elliptical driving sector and an ellipticaldriven gear as one embodiment of my invention, it is to be understoodthat any gear mechanism which has a variable radius such that a maximumspeed is produced intermediate slow speed positions could be used inplace of the gear construction shown. A few examples are heart gears,sinusoidal gears or square gears. Furthermore, although I have indicatedthe actuating mechanism as including a pair of Bourdon tubes of theself-draining type, it is to be understood that such actuating meanscould well include a single Bourdon tube or some other pressureresponsive element. Elements of the disclosed embodiment such. as theressure responsive element, the gauge casing, etc., form no part of myinvention and may be of conventional design.

While I have described a particular embodiment of my invention it is tobe understood that I do not wish to be restricted thereto and that Iintend to cover all modifications thereof which would be evidentto oneskilled in the art and which fall within the true spirit and scope ofthe appended claims.

Having described my invention, what Iclaim as new and wish to secure byLetters Patent is:

1. A pressure gauge comprising, in combination, dual pressure responsiveelements movable in opposite directions, a rotatable sector connected tobe actuated by said pressure responsive elements, said sector having atleast one major and two minor radii, a rotatable gear driven by saidrotatable sector, said gear having at least one minor and two majorradii, the gear radii being substantially at right angles to thecorresponding radii of the driving sector whereby a variable speedrotation is imparted to the rotatable gear, a pressure scale, andindicating means actuated by said rotatable gear to traverse saidpressure scale.

2. A pressure gauge comprising, in combination, dual pressure responsiveelements movable simultaneously in opposite directions, an ellipti calsector connected to be actuated by said dual pressure responsiveelements, an elliptical gear driven by said elliptical sector, said gearhaving an indicator rigidly ailixed thereto, and a pressure indicatingdial traversed by said indicator.

3. A pressure gauge comprising, in combiner tion, dual Bourdon tubesmovable in response to variations in pressure, an elliptical sector,means including links in connection with said sector and connected to beactuated by said dual Bourdon tubes for driving said sector, anelliptical gear driven by said sector, an indicator rigidly amxed tosaid gear, and a pressure indicating dial traversed by said indicator.

4. A pressure gauge comprising in combination dual pressure responsiveelements movable simultaneously in opposite directions, an ellipticalsector connected to be actuated by said dual pressure responsiveelements, a graduated dial, the graduations on said dial being spacedprogressively farther apart from each other from the end graduations toa point intermediate thereof, an indicator adapted to traversesaidgraduated dial and means connected to be actuated by said ellipticalsector for actuating said indicator across said dial at a speed varyingin accordance with said gradnations.

5. A pressure gauge comprising in combination dual pressure responsiveelements movable simultaneously in opposite directions, an ellipticalsector connected to be actuated by said dual pressure responsiveelements, a graduated dial, the graduations on said dial being spacedprogressively farther apart from each other from the end graduations toa point intermediate thereof, an indicator adapted totraverse saidgraduated dial, and an elliptical gear driven by said sector, saidindicator being aflixed to and adapted to be actuated by said gearacross said-dial at a speed varying in accordance with said graduations.

6. A pressure gauge comprising in combination dual pressure responsiveelements movable simultaneously in opposite directions, a rotatableelliptical sector, means including a lever for rotating said sector,said means actuated by said pressure responsive elements, a graduateddial, the graduations on said dial being spaced progressively fartherapart from each other from the end graduations to a point intermediatethereof, an indicator adapted to traverse said dial and means connectingsaid indicator with said sector, said last-mentioned means adapted toactuate said indicator across said dial at a speed varying in accordancewith said sraduations.

7. A pressure gauge comprising in combination dual pressure responsiveelements movable simultaneously in opposite directions, a rotatableelliptical sector, linkage means including a lever for rotating saidsector. said means connected to be actuated by said pressure responsiveelements,

a graduated dial. the graduations on said dial being spacedprogressively farther apart from each other from the end graduations toa point intermediate thereof, a gear driven by said sector, and anindicator amxed to said gear, said gear being adapted to actuate saidindicator across said dial at a speed varying in accordance with saidgraduations.

JOHN W. MARSH.

